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The workability and the de-airing behaviour of fresh concrete are strongly influenced by the cement paste contained therein. The rheological properties of cement pastes and concretes in general are a function of the mix composition, hydration processes, shear history and external influences (such as temperature, vibration etc.). Microscopic interparticle interactions control the macroscopic bulk rheology. In the paper at hand, the results of a 6-year project are described, in which the interactions between particles, between particles and the carrier liquid, as well as superplasticizers and variations in particle inventory and the carrier fluid composition, were studied. The work in the first step yielded in a surface complexation model for a cement paste model system, which allows to predict the particles’ zeta potential and other surface parameters as a function of the ion brine composition. Further, an in-depth analysis of the mechanisms of thixotropy in cementitious suspensions was carried out and a corresponding model was developed. This model is based on the results of combined rheological and tomographical measurements. In doing so, a prediction of the rheological properties of cement suspensions subjected to a complex shear history during the entire lifetime of fresh cement suspension is now possible. The prediction of the rheological properties becomes even more challenging when Ordinary Portland Cement (OPC) is replaced by supplementary cementitious materials (SCMs) like calcined clays, where the clay composition and its calcination conditions significantly influence the flow behaviour and the entire hydration process. The analysis of calcination conditions for varying clay mineralogy and the influence of SCMs on the hydration processes of OPC ensure an extended application of the findings for low-clinker concrete. Concerning the practical application of the results, the effect of the rheological properties of the paste on the de-airing behaviour of concrete was investigated and modelled. A proper de-airing process of fresh concrete can be achieved by tuning the predicted rheological properties of cement paste.

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Component Additive Approach to Predict Cement Paste Rheology Considering Heterogeneities on Different Scales and Supplementary Cementitious Materials and Their Special Effect on Thixotropy and Concrete De-airing Behaviour (CONCERT & CONCERT-CCair)

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  • 出版模式：

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  • 发表日期：

    2026年

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  • J. Link,
  • S. Hellmann,
  • B. Strybny,
  • C. Hoffmann,
  • T. Sowoidnich,
  • C. Rößler,
  • T. Gil Díaz,
  • J. Lützenkirchen,
  • F. Heberling,
  • D. Jara Heredia,
  • H. M. Ludwig,
  • T. Schäfer,
  • M. Haist

摘要

The workability and the de-airing behaviour of fresh concrete are strongly influenced by the cement paste contained therein. The rheological properties of cement pastes and concretes in general are a function of the mix composition, hydration processes, shear history and external influences (such as temperature, vibration etc.). Microscopic interparticle interactions control the macroscopic bulk rheology. In the paper at hand, the results of a 6-year project are described, in which the interactions between particles, between particles and the carrier liquid, as well as superplasticizers and variations in particle inventory and the carrier fluid composition, were studied. The work in the first step yielded in a surface complexation model for a cement paste model system, which allows to predict the particles’ zeta potential and other surface parameters as a function of the ion brine composition. Further, an in-depth analysis of the mechanisms of thixotropy in cementitious suspensions was carried out and a corresponding model was developed. This model is based on the results of combined rheological and tomographical measurements. In doing so, a prediction of the rheological properties of cement suspensions subjected to a complex shear history during the entire lifetime of fresh cement suspension is now possible. The prediction of the rheological properties becomes even more challenging when Ordinary Portland Cement (OPC) is replaced by supplementary cementitious materials (SCMs) like calcined clays, where the clay composition and its calcination conditions significantly influence the flow behaviour and the entire hydration process. The analysis of calcination conditions for varying clay mineralogy and the influence of SCMs on the hydration processes of OPC ensure an extended application of the findings for low-clinker concrete. Concerning the practical application of the results, the effect of the rheological properties of the paste on the de-airing behaviour of concrete was investigated and modelled. A proper de-airing process of fresh concrete can be achieved by tuning the predicted rheological properties of cement paste.